Flexible high-strength wire-reinforced rubber hoses

ABSTRACT

In a flexible high-strength fiber-reinforced rubber hose having a plurality of reinforcing wire plies, a well defined relation is established between the wrapping angles of the plies the essence of which is that the angle difference between the plies of higher pitches is smaller than the angle difference between the angles of plies of smaller pitches, while the angles satisfy well defined relations.

[ Apr.24, 1973 FLEXIBLE HIGH-STRENGTH WllRE- REINFORCED RUBBER HOSES a aH m e S U r b m A Inventors: Laszlo Horvath; Gusztav Gundisch;

Mihaly Arvai; Sandor Antal, all of Budapest, Hungary PrimaryExaminerMeyer Perlin Assistant Examiner-Ronald C. Capossela [73]Assignee: Orszagos Gumiipari Vallalat, Bu- Att0rney-Y0ung&ThOmpSOndapest V111, Hungary June 10, 1971 Appl. No.: 151,739

ABSTRACT 22 Filed:

[52] US. Cl...................l38/130,138/131, 138/133,

F1 11/00 angle difference between the plies of higher pitches is 2; 130131 smaller than the angle difference between the angles of plies ofsmaller pitches, while the angles satisfy well defined relations.

5 Claims, 3 Drawing Figures [56] References Cited UNITED STATES PATENTSO 0 1 I 0 0 0 0 0 Q 0 a $4 a 0 4a 3 Sheets-Sheet 2 Patented April 24,1973 Patented April 24, 1973 3,729,028

3 Sheets-Sheet 5 Fig.3

FLEXIBLE HIGH-STRENGTH WIRE-REINFORCED This invention relates toflexible high-strength fiberreinforced rubber hoses.

As is known, such rubber hoses have to cope with ever increasingrequirements which prescribe, at present, internal diameters of 100millimeters and more, and a suitability for internal pressures of up to700 absolute atmospheres. Moreover, for special purposes rubber hosesare needed which have to withstand an additional external pressure of300 absolute atmospheres and an axially acting force of 300 tons, and

are suitable for being loaded by a torque of upto 2,000 meter-kiloponds.

Since conventional rubber hoses are unsuitable for bearing such loads,it has been suggested to form rubber hoses of a plurality of circularlywoven superposed plies. However, the life period or durability of suchrubber hoses is insufficient. This is due to their braided fibers beingmutually rubbed under-the action of internal pressure which, generally,appears in the form of surges.

Another known suggestion consists in employing plies the fibers of whichshow alternately opposite hands. However, with such rubber hoses it isvery difficult to ensure co-operation of plies of different diameters.In addition, they show a relatively high torsion underloads.

It has been suggested to improve the co-operation of the plies of suchrubber hoses by deviating from the conventional pitch angle of 3516 tothe hose axis which has been held ideal. For this purpose eitherpairwise similar angles have conventionally been selected or but slightangle differences have been employed between associated plies. Suchexpedients, however, failed to ensure good co-operation of the plies ina satisfactory manner. Moreover, the arising forces considerably differfrom one another and measuring data show variations from 50 to 300percent.

BRIEF SUMMARY OF THE INVENTION The main object of the present inventionis to obviate such deficiencies and to provide flexible high-strengthwire-reinforced rubber hoses the plies of which show a desiredco-operation under service conditions. In order to ascertain the sourcesof the aforesaid deficiencies various investigations have been made:

A rubber hose comprising a pair of plies wrapped at an angle of theconventional value of 3516 has been exposed to pressure. Thereupon, therubber hose showed a considerable torsional deflection at aninsignificant change of length. The torsional deflection alreadyappeared at relatively low pressures in the range of 25 to 50atmospheres whereafter its changes with increasing pressure werenegligible. The direction of torsion was always such that the upper plybecame constricted. Such behavior of the rubber hose may perhaps beexplained by the technology of manufacture of rubber hoses which impliesthat co-operation between the plies may be obtained only after a certainconstriction because during the manufacturing procedure there is alwayssome residual looseness in the structure of the rubber hose due tomutual recession of its plies. Constriction results because the diameterof the internal ply increases upon torsional deflection while thediameter of the external ply decreases. Constriction amounts to about0.1 to 0.8 millimeter in case of thoroughly constructedrubber hoseshaving diameters in the range of 76 to I01 millimeters.

Thus, with double ply rubber hoses co-operation of the plies is obtainedby torsional deflection although the loads therein will not be uniformand experiments have shown that the difference between the loads amountsto about 50 percent so that it must not be neglected.

With high pressure rubber hoses having a plurality of plies thedifficulties are still greater since constriction between the variousplies is not always obtained by torsional deflection. For instance, incase of a four-ply rubber hose in which the plies were alternatelywrapped at opposite hands and at uniform angles, or were wrappedpairwise at the same angle, the lowermost ply would show outwardtorsional deflection while the second ply would be deflected inwardlyupon internal pressure. Thus, the interstice between the first andsecond ply would-decrease. However, the first ply caused through thefitting or coupling of the rubber hose the third ply of similar hand toflare whereby the diameter of the latter increased. Since the diameterof the second ply decreased, no constriction necessary for co-operationcould be obtained between the second and third ply.

In summary, differences between the loads in the plies and distortionsunder such loads are due to three circumstances. First, a constrictionof the plies under load cannot entirely be eliminated even if the bestknown'method is employed for manufacture. Secondly, torsional deflectiondoes not produce uniform loads in the plies. Moreover, it is responsiblefor shearing forces by which the useful life of the hoses is materiallylimited. Third, the reinforcing wire plies of heavy-duty rubber hosesmay be manufactured but of materials of extraordinarily low elongationwhich means that materials with practically no elongation at all will beemployed. Consequently, there will be no elongations of such materialswhich would permit a compensation of load differences between the pliesof a rubber hose.

Thus, the only expedient to bring about constriction between the pliesof a rubber hose and uniformity of ply loads is the variation of thehose length. For such purpose, however, the plies have to be wrapped atvarious angles the variation of which is such that upon change of thelength plies of higher pitches will vary in diameter more than those ofsmaller pitches. A further consideration consists in that with thelowermost ply or with the lower plies of a rubber hose being wrapped atan angle greater than the conventional value of 3516 the rubber hosewill become shorter upon internal pressure whereas the plies beingwrapped at angles smaller than the aforesaid value the length of therubber hose will increase.

It has now been ascertained that a desired uniform constriction and loaddistribution between the plies due to length variations may be obtainedif the pitches of the plies of rubber hoses of the shortening typedecrease and the pitches of the plies of rubber hoses of the lengtheningtype increase radially outward in such a manner that the angledifference between the plies of higher pitches is smaller than thedifference between the angles of the plies of smaller pitches and thisis the essence of the invention. It can be shown that for threesuperposed plies such requirement means a relation in which:

where D, D,, D designate original diameters,

D; D,, D designate changed diameters, and

j designates the serial number of a ply in a radially outward direction.

Relation (l) which has to be fulfilled by further plies as well means incase of rubber hoses of more than three wire-reinforced plies that thedifference between the diameter changes of the first two plies should beequal to the difference between the diameter changes of the second twoplies. Calculations based on relation (1) result in the followingrelation between the wrapping angles of three superposed plies:

D tan oz +D, ,tan o+1= 2D tan a 2) where a is the angle of the ply wiresto the hose axis.

The wrapping angles of further plies are calculated in a similar manner.

Relation (2) establishes a strict interdependence between the wrappingangles of superposed plies in a group of such plies. However, it hasbeen found that further requirements have to be met if uniformconstrictions and load distribution between the plies are desired.First, both extreme angles, i.e., the wrapping angles of the innermostply and the outermost ply have to be selected according to the leastdifference between the strains in the individual plies, the strainsthemselves being ascertained by measurements. Secondly, it has to beconsidered as well that rubber hoses having plies of great wrappingangles approaching 90 are less flexible which means relatively higherstresses upon being incurved. Thirdly, the greater the differencebetween the wrapping angles, the lesser the length variation requiredfor the constriction of the plies.

Such considerations show that in case of rubber hoses with at leastthree superposed plies the difference between both extreme angles shalllie in the range of 6 to 80 while the intermediate angles are to beselected so that they satisfy relation (2). Then the difference betweenthe diameter changes will be responsible for a constriction of 0.1 to0.8 millimeter. Thus, in its broadest terms, the invention is concernedwith flexible high-strength wire-reinforced rubber hoses comprising aplurality of load-bearing wire plies incorporated therein, each wire plybeing formed ofa multiplicity of individual resiliently flexible wiresdisposed in helical convolutions about the longitudinal axis of the hosein a manner known per se. The invention proper consists in that theinnermost wire ply and the outermost wire ply are wrapped at angles tothe hose axis the difference of which lies within the range of 6 to 80'while the wrapping angles of three contiguous plies satisfy theaforesaid relation (2).

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described ingreater detail by reference to the accompanying drawings the FIGS. 1 to3 of which show perspective views of exemplified hose constructionsaccording to the invention, the component portions of the hose coversbeing broken away progressively to illustrate the nature of the severalcomponents.

Same reference characters designate similar details throughout thedrawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to thedrawings, FIG. 1 shows a rubber hose having four superposed wire plies10, 12, 14, 16, each wire ply being composed of a multiplicity ofindividual fine high tensile wires disposed in parallel helicalconvolutions about the longitudinal axis I I of the hose. The helicesare of opposite hands in extreme pairs of wire plies 10, 12 and 14, 16,respectively. The several wire plies 10, 12, 14, 16 are insulated fromone another in a manner known per se by means of layers of, e.g.,rubberized cloth 18,20 and 22, respectively. A pressure distributorlayer 26 made of non-metallic fabric underlies the innermost wire ply l0and, in turn, encloses a rubber tube 28. On the other hand, wire ply 16is surrounded by a layer 30 made likewise of nonmetallic fabric which,in turn, underlies an outer rubber cover 32.

In compliance with the present invention, relations (2) requires that Dtan oz D Ian a 2D tan 0z and where and If it is desired that the rubberhose have equal burst resistance and tensile strength which means equalradial and axial load carrying capacities, the wrapping angles have tosatisfy a further relation which requires that sin a sin a .+sin a,,=(n/3)X(OX21 tXT/PXDX) and The directions of the fibers in the plies haveto be selected in consideration of torsional deflection. E.g., in caseof the exemplified four-ply rubber hose both intermediate plies 12 and14 are unidirectional while both extreme plies l and 16 are of theopposite hand. If in the course of the manufacturing procedure thedimensions of such rubber hose deviate from the calculated values, adeflection of the first ply l0 tries to constrict the third ply 14through the fitting or (not shown) of the hose. Then, a slight recessionbetween the second (fourth) ply 12 or 16 and the third ply 14 will beexperienced as if the third ply were unidirectional with the first ply10. I

Such new rubber hose structure may be'called A B B A type arrangementwhere A designates a selected direction and B designates the oppositehand. In addition to its above mentioned advantage of favorable responseto torsional deflection it has the further advantage of the meandiameter of the pairs of plies of opposite hands being exactly thesame.Such uniformity of both mean diameters results in circumstances similarto those of circularly woven or braided plies yet without the undesiredweakening action of mutually rubbing wires.

FIG. 2 illustrates, by way of example, an embodiment which differs fromthe previous one in two respects. First, it has three reinforcing wireplies instead of four, and, secondly, one of them is a ply 34 consistingof the convolutions of one helical wire of rectangular crosssectionalarea 34a instead of a multiplicity of individual wires. Thus, wireply 34which is substituted for wire ply 10 of the previous exemplifiedembodiment has a high moment of inertia of at least five times themoment of inertia of the other wire plies 12 and 14 at a mean diameterof D and at a small wrapping angle a, of at most lf relation (3) issatisfied by the various parameters of such rubber hose, it will besuitable to withstand, in addition to internal and external pressures asin the former case, big axial surplus loads due to excessive lengthssuch as required in deep drilling where rubber hoses have to beserviceable at depths of 3,000 meters and more. It has been found thatin such cases, the crushing action of the big axial surplus load will beborne by the innermost ply 34 of the system formed by a helix ofspecified construction.

FIG. 3 represents an exemplified embodiment where the series of pliesdegenerates, as it were, to a single pair of wire plies such as plies l0and 12 of the embodiment shown in FlG. 1. However, the basic idea ofensuring uniform loads in both plies l0 and 12 by the compensatingeffect of length variations is obtainable here as well if the differenceof the wrapping angles a, and 0 of the plies and 12, respectively, isselected so as to lie in a range of 2 to 8 while the mean value of thewrapping angles differs by at least 10 minutes from the conventionalvalue of 35l 6. This means that:

2 el -a 8 and In general terms, double-ply rubber hoses made incompliance with the present invention will have a 5 wrapping angledifference which lies in the range of 2 to 8. Dependent on whetherrubber hoses of the shortening or lengthening type have to be produced,the mean value of both angles will be greater or smaller by l() minutesthan the conventional value of 35l 6'.

The distortions in operation of big high strength rubber hoses can befurther decreased. It has been found that distortions take place atrelatively small pressures. Therefore, it is suggested that the rubberhoses be in the course of their manufacture put under internal pressureprior to their being cured whereby their plies will be constricted dueto length variation prior to curing and, thus, they will be fixed insuch position when cured so that distortions in service will decrease topractically negligible extents.

It has been shown that similar constrictions within the plies can beobtained with both shortening and lengthening rubber hose types.Generally, the use of the shortening type rubber hoses will be preferredsince their behavior and bending properties are more favorable. However,if the stresses of the rubber hose comprise big axial loads and torques,preferably rubber hoses of the lengthening type will be used.

What we claim is:

1. A flexible high-strength fiber-reinforced rubber hose, comprising aplurality of load-bearing wire plies incorporated therein, each wire plybeing formed of a multiplicity of individual resiliently flexible wiresdisposed in helical convolutions about the longitudinal axis of thehose, the outermost wire plies being at angles to the hose axis thedifference between which amounts to 6 to 80 and the angles of threecontiguous wire plies satisfying the following equation:

where D D,, and D, are the diameters of the three contiguous wire plies,respectively,

(1 0:, and a, are the angles of the respective wire plies to the hoseaxis, and

j is the serial number of any intermediate wire ply.

2. ln a flexible high-strength fiber-reinforced rubber hose as claimedin claim 1 the improvement of one of the wire plies being a helicalsteel spring.

3. In a flexible high-strength fiber-reinforced rubber hose as claimedin claim 1 the improvement of at least two contiguous wire plies havinghelical convolutions of the same hand.

4. A flexible high-strength fiber-reinforced rubber hose comprising twoload-bearing wire plies incorporated therein, each wire ply being formedof a multiplicity of individual resiliently flexible wires disposed inhelical convolutions about the longitudinal axis of the hose, both wireplies having angles to the hose axis the difference of which liesbetween 2 to 8, the average of the angles being different by at least 10minutes from the value of 3516.

5. In a flexible high-strength fiber-reinforced rubber hose as claimedin claim 1 the improvement in which the wrapping angles of all wireplies satisfy the following equation:

sin' oz sin a sin a (n/3)(0.21 1 T)/(P- T designates the sum of axialexternal forces loading D) the individual plies in kiloponds, where Pdesignates the forces appearing in the wire plies in a 01,, designatewrapping angles, 5 d klloponds n designates the number of reinforcingplies, an h t designates the distance between wire centers of a Ddeslgnates the mean lameter oft e wlre phes m pair of contiguousconvolutions in a fiber-reincennmeers' forced ply in centimeters,

1. A flexible high-strength fiber-reinforced rubber hose, comprising aplurality of load-bearing wire plies incorporated therein, each wire plybeing formed of a multiplicity of individual resiliently flexible wiresdisposed in helical convolutions about the longitudinal axis of thehose, the outermost wire plies being at angles to the hose axis thedifference between which amounts to 6* to 80* and the angles of threecontiguous wire plies satisfying the following equation: Dj 1tan2 Alphaj 1 + Dj 1tan2 Alpha j 1 2 Djtan2 Alpha j where Dj 1, Dj, and Dj 1 arethe diameters of the three contiguous wire plies, respectively, Alpha j1, Alpha j and Alpha j 1 are the angles of the respective wire plies tothe hose axis, and j is the serial number of any intermediate wire ply.2. In a flexible high-strength fiber-reinforced rubber hose as claimedin claim 1 the improvement of one of the wire plies being a helicalsteel spring.
 3. In a flexible high-strength fiber-reinforced rubberhose as claimed in claim 1 the improvement of at least two contiguouswire plies having helical convolutions of the same hand.
 4. A flexiblehigh-strength fiber-reinforced rubber hose comprising two load-bearingwire plies incorporated therein, each wire ply being formed of amultiplicity of individual resiliently flexible wires disposed inhelical convolutions about the longitudinal axis of the hose, both wireplies having angles to the hose axis the difference of which liesbetween 2* to 8*, the average of the angles being different by at least10 minutes from the value of 35*16''.
 5. In a flexible high-strengthfiber-reinforced rubber hose as claimed in claim 1 the improvement inwhich the wrapping angles of all wire plies satisfy the followingequation: sin2 Alpha 1 + sin2 Alpha 2 + . . . + sin2 Alpha n (n/3)-(0.21 . t . T)/(P . D) where Alpha 1, Alpha 2 . . . , Alpha n designatewrapping angles, n designates the number of reinforcing plies, tdesignates the distance between wire centers of a pair of contiguousconvolutions in a fiber-reinforced ply in centimeters, T designates thesum of axial external forces loading the individual plies in kiloponds,P designates the forces appearing in the wire plies in kiloponds and Ddesignates the mean diameter of the wire plies in centimeters.